Method for producing foundry casting molds

ABSTRACT

A method for producing casting molds, such as cores or core assemblies used in foundry practice, wherein molding material, preferably molding sand, is injected or shot into a molding chamber via a gaseous flow medium, preferably air, under a predeterminable pressure. The shot and resulting solidified mold is deaerated, then the tool is opened, and the solidified mold is removed. The shooting process and/or deaeration process are controlled via detected and, if need be, prepared process parameters according to a predeterminable specification.

CROSS REFERENCE TO RELATED APPLICATION

[0001] This is a continuation of international applicationPCT/DE00/03870 filed Nov. 3, 2000, and designating the U.S.

BACKGROUND OF THE INVENTION

[0002] The invention relates to a method for producing casting molds,such as cores or core assemblies used in foundry practice, whereinmolding material, preferably molding sand is injected or shot via agaseous flow medium, preferably via air, under a predeterminablepressure, into a molding chamber. The shot and resulting solidified moldis then deaerated, the tool is opened, and the shot mold is removedafter opening the tool.

[0003] Quite generally, the invention relates to the field of foundrypractice. For casting shaped parts of any type, foundry cores or foundrymolds are generally made as separate parts, combined, and joinedtogether to form a casting mold or a core assembly. Thereafter, thesecore assemblies are filled with molten metal for producing, for example,a metallic workpiece. In series production, the core assemblies to befilled with molten metal pass one after the other through the productionline.

[0004] Core and shell shooting machines of the above type have beenknown from practice for decades. Only as an example, one may refer to DE31 48 461 C1, which discloses a core and shell shooting machine.

[0005] Until now, production of ready-to-pour shells or core assemblieshas occurred from a control device or control panel, wherein productionis predetermined by a constant control. In the case of a change in theproduction sequence or in the case of a change in individual productionsteps or production stations, it has been necessary to change or adjustthe control. An automatic monitoring or even adjustment of theproduction process, in particular the actual shooting operation, viadeaeration, until the removal of the shot core, has been absent.

[0006] In the shooting of casting molds, it is possible that on the onehand during the actual shooting operation, and on the other hand duringthe deaeration and subsequent opening of the mold, very crucial problemsarise, which counteract an optimization of the production process. Thus,for example, individual shooting nozzles and/or deaeration nozzles mayclog with core sand, so that a longer process duration or an inadequateoutcome of the production process is bound to result. Tool wear ordamage to the tool likewise counteract an optimal production outcome. Atoo rapid deaeration of the shooting hood after the shooting operationcould cause sand to whirl up or flow back, thereby negatively affectingon the one hand the outcome of the production and on the other hand theproduction quality, in particular, however, also the cycle time.

[0007] DE 44 22 353 C2 discloses a method for producing casting molds orparts of such molds, wherein the injecting or shooting operation isterminated at a time, which is a function of the pressure in the moldingchamber. Specifically, in the cited art the injecting operation isterminated, when the pressure in the molding chamber has passed througha maximum. Accordingly, the maximum pressure is an indication forterminating the injecting operation. Further parameters are notconsidered in the art.

[0008] In practice, however, the method disclosed in DE 44 22 353 C2 isproblematic, since only a pressure maximum is detected. For example, ifa pressure maximum develops in the case of increasingly cloggingnozzles, the injecting operation is ended, without an adequate shapinghaving been able to take place. In the end, the known method involves acontrol, with the parameter used for the control being the pressuremaximum within the molding chamber.

[0009] It is therefore an object of the present invention to furtherdevelop a method of the described general type, so that for the qualityassurance, a monitoring of the process occurs with simple means.

SUMMARY OF THE INVENTION

[0010] The method of the present invention accomplishes the foregoingobject in that the shooting process and/or the deaeration process arecontrolled in response to at least one process parameter that isdetected and compared in accordance with a predeterminablespecification. Contrary to the general state of the art, no control willoccur upon detection of a maximum pressure. Instead, an adjustment ismade, which is based on process parameters according to anypredeterminable specification. Affected are at least the processes ofthe actual shooting and deaeration before removing the shot andsolidified mold. The goal of such an adjustment is the reduction of thecycle time, the automation of the production process, as well as thedetection of defects or imperfections via conclusions from the processparameters and the cycle times resulting therefrom.

[0011] Specifically, it would be possible to base the adjustment onindividual process parameters, predeterminable combinations of theprocess parameters, or algorithms on the basis of the processparameters. Furthermore, it would be possible to predetermine for therespective process step or process, i.e. for the actual shooting and/orfor the deaeration, a maximum process duration as special processparameters. Should a longer process duration result or be computed basedon the other process parameters, one would be able to infer a defect,for example, clogged nozzles, imperfections on the tool, or the like.What matters in the end are the detected parameters, which allow to drawthe different conclusions as to the quality of the production and/or thecondition of the tool.

[0012] At this point, it should be especially emphasized that it ispossible to detect as a process parameter the pressure, which builds upor prevails in the entire system during the shooting. Specifically, itmay be the pressure in the shooting air reservoir, in the sand hopper,in the tool, in the lines, or elsewhere in the system. Contrary to acontrol upon reaching a predetermined or predeterminable maximumpressure, one could use here as a basis a pressure progression in aregular shooting process, which is used to compare the actual pressureprogression over the shooting process. Should the actual pressureprogression deviate from the predetermined pressure progression, itwould be possible to lengthen or shorten the duration of the shootingprocess via a corresponding adjustment, namely depending on the kind andamount of the deviation.

[0013] As an alternative or in addition to the detection of the pressureor pressure progression, it would be possible to detect as a furtherprocess parameter during the shooting, the volume flow or air flow inthe entire system, for example, in the tool. Likewise in this instance,it would be possible to take a progression of the volume flow or airflow extending over the entire shooting process as a basis for areference input, so that in the case of a deviation from desired values,an adjustment is made, which lastly becomes effective on the timecharacteristic and/or the required pressure. An increasing clogging ofthe shooting nozzles could be counteracted, at least within a certainscope, by a pressure increase.

[0014] It is likewise possible to detect as a process parameter thequantity of sand that is injected into the tool. This may occur, forexample, via a weight loss in the supply container or via a weightincrease in the tool or molding chamber. It would be possible to end theshooting process based on a plurality of process parameters, namelywhile taking into account the concrete sequence of the processparameters over the production process.

[0015] It is likewise possible to adjust the course of the deaerationprocess and, if need be, the time of opening the tool via detected and,if need be, prepared process parameters, namely similarly to the case ofthe actual shooting process. During the deaeration of the tool, it wouldbe possible to detect as a process parameter the pressure progressioninside the tool, and to compare it with a predetermined pressureprogression in the case of an ideally completed deaeration.

[0016] Furthermore, it is possible to detect as process parameter duringthe deaeration of the tool, the air flow, in particular the amount ofair flowing out of the tool. As soon as a predeterminable quantity ofair has escaped, it will be possible to open the tool, with thisprocedure being dependent on the inner volume of the tool.

[0017] Within the scope of an especially advantageous development of themethod according to the invention, a preferably electromagneticallyoperating air bleed valve is activated in such a manner that, whileavoiding sudden changes of pressure, the pressure prevailing in the tooldrops gradually. A linear pressure drop has shown to be especiallyadvantageous for purposes of effectively avoiding that sand particlesare entrained toward the air bleed valve or backward into the shootingnozzles. It is here intended to effectively avoid clogging by entrainedsand particles.

[0018] Furthermore, it would be possible to compare the individualproduction steps or processes and/or the detected and/or determinedprocess parameters with an optimal curve of the process sequence,preferably via a graph that can be shown on a display. Within the scopeof such a development, it is possible to perform an optical comparisonwith reference to two curves. In this process, an operator may interveneinteractively by adjustment, namely based on the comparison or possibledeviations. Likewise possible is an automatic adaptation in the case ofcorresponding deviations. Such an adaptation is regularly effective onthe time characteristic of the process.

[0019] As earlier mentioned, it would be possible to determine the idealprocess duration based on the detected and/or determined processparameters. In this process, attempts are made to minimize the cycletime. For example, one could thus predetermine that upon exceeding apredeterminable cycle time, maintenance is performed or a tool exchangeoccurs.

[0020] In any case, it is basically possible that based on the detectedand/or determined process parameters, the respective process ismonitored with respect to possible imperfections or defects on the toolor on the machine itself. Lastly, there exists the possibility ofdrawing conclusions via the determined and, if need be, prepared processparameters, as to the quality of the production and/or the condition ofthe tool or the machine. Using the detected and/or determined processparameters as a basis, it also possible to define, for example, theideal time for an automatic tool change, so that a least possible cycletime is realizable with an always functioning tool. It is likewisepossible to compute the optimal maintenance interval based on thedetected and/or determined process parameters, so that also to thisextent, it is possible to realize a minimization of the cycle time,primarily, however, also a minimization of unnecessary repair workbecause of a regular and adequate maintenance.

[0021] Finally, it should be expressly stated that the foregoingdescription of the preferred embodiments of the invention does not limitthe invention beyond the claims.

1. A method for producing casting molds adapted for use in foundrypractice, comprising the steps of shooting a molding material via agaseous flow medium under a predeterminable pressure into a moldingchamber, causing the molding material to solidify in the molding chamberand form a solidified mold, deaerating the solidified mold, opening themolding chamber, removing the solidified mold from the opened moldingchamber, and controlling the shooting step and/or the deaeration step inresponse to at least one detected process parameter compared to apredeterminable specification.
 2. The method of claim 1 wherein thecontrolling step is based on individual process parameters,predeterminable combinations of the process parameters, or algorithms onthe basis of the process parameters.
 3. The method of claim 1 wherein amaximum process duration is predetermined as the process parameter. 4.The method of claim 1 wherein the pressure, which builds up or prevailsduring the shooting step in the system is detected as the processparameter.
 5. The method of claim 1 wherein during the shooting step,the volume, flow or the air flow at desired places in the system isdetected as the process parameter.
 6. The method of claim 1 whereinduring the shooting step the quantity of the injected molding materialis detected as the process parameter.
 7. The method of claim 1 whereinthe duration of the deaeration step and/or the time of opening themolding chamber are adjusted via the detected and/or a prepared processparameter.
 8. The method of claim 1 wherein during the deaeration step,the pressure progression within the molding chamber is detected as theprocess parameter.
 9. The method of claim 1 wherein during thedeaeration step the air flow leaving the molding chamber is detected asthe process parameter.
 10. The method of claim 1 wherein during thedeaeration step an electromagnetically operating air bleed valve isactivated in such a manner that the pressure prevailing in the moldingchamber drops, while avoiding sudden pressure changes.
 11. The method ofclaim 1 wherein the controlling step includes comparing the detectedprocess parameter with an optimal curve of a process sequence via agraph that can be shown on a display.
 12. The method of claim 11 whereinthe controlling step further includes influencing the individual processsteps interactively or automatically, using as a basis the comparison orpossible deviations thereof.
 13. The method of claim 1 wherein the idealprocess duration is determined, using as a basis the detected and/ordetermined process parameters.
 14. The method of claim 1 wherein therespective process steps are monitored for possible imperfections ordefects, using as a basis the detected and/or determined processparameters.
 15. The method of claim 1 wherein the time for an automatictool change is defined, using as a basis the detected and/or determinedprocess parameters.
 16. The method of claim 1 wherein the maintenanceinterval is computed, using as a basis the detected and/or determinedprocess parameters.